1. Field of the Invention
This invention relates to a Thermos or vacuum bottle equipped with an electric heater for boiling or heating water or the like contained therein.
2. Prior Art
A conventional vacuum bottle comprises a body including a pair of inner and outer shells spaced from each other to provide a thermal insulation space therebetween which is evacuated, and an electric heater disposed within the inner shell for heating the contents thereof. The bottoms of the inner and outer shells partly overlap each other, and apertures are formed respectively through the overlapping portions of the shell bottoms and disposed in alignment with each other. The lower portion of the electric heater extends through the aligned apertures of the shell bottoms, and a sealing element is provided between the bottom of the inner shell and the lower portion of the electric heater to provide a liquid-tight seal therebetween. With this construction, for assembling the vacuum bottle, it is necessary that the respective apertures of the two shell bottoms should be brought into alignment with each other so that the lower portion of the electric heater can be properly passed therethrough. Therefore, close manufacturing tolerances are required for the inner and outer shells. In addition, much effort is required for the assembly of the vacuum bottle in the case where the apertures of the shell bottoms are not accurately in alignment with each other. It has also been proposed to space the bottoms of the inner and outer shells from each other. However, with the conventional vacuum bottle, it has been difficult to provide a sufficient spacing between the two bottoms, so that the heat can be easily transferred from the inner shell via the outer shell to the exterior of the vacuum bottle, which results in the failure to provide a good thermal insulation of the vacuum bottle.